The invention relates to an ultrathin chemically grown oxide layer which serves to prevent dopant diffusion between semiconductor layers.
P-type and n-type dopants are added to semiconductor material, notably silicon, to enhance conductivity. Most semiconductor devices require adjacent regions of the device to have different dopant characteristics: One region is to be heavily doped while an adjacent region is undoped or lightly doped, for example; or a heavily doped p-type region may be adjacent to a heavily doped n-type region.
Dopants do not reliably remain where they've been placed through implantation or in situ doping, however. Dopants tend to diffuse, and, particularly in smaller devices, sharp transitions in doping profiles can be difficult to maintain.
Barriers can be used to prevent dopant diffusion, but in general such barriers will significantly change the electrical properties of the device. A thick oxide layer, for example, would form an unwanted dielectric barrier.
There is a need, therefore, for a method to prevent or inhibit dopant diffusion between semiconductor regions in a semiconductor device without disrupting the electrical function of the device.